So just to play, for a single person 50% of $2000 is a max credit of $1000:
$17,750 - Max AGI for 50%
-$6,100 - Standard Deduction
-$9,900 - Personal Exemptions
=7,750 taxable income which is all taxed at 10%
x 10%
=$775 taxes
So you're losing out on $225 of the credit
Head of Household, max credit is still $1000
$26,625 - Max AGI for 50%
-$8,950
-$7,800 Personal exemptions (assuming one kid)
=9,875 taxable income which is all taxed at 10%
x 10%
=$988 Taxes
So you're only losing out on 12 of the credit this way...